PhosphorRTTY

PhosphorRTTY decodes Radio Teletype (RTTY) signals in real time using your iPhone or iPad microphone. Hold it near a shortwave radio tuned to an RTTY signal and watch the text appear on screen, character by character, on an authentic phosphor CRT display.

No internet connection required. No external hardware. No account. Just your iPhone or iPad and a radio.

WHAT IT DECODES

RTTY is the oldest digital mode in amateur radio: two audio tones representing mark and space, encoding text via the 5-bit ITA2 (Baudot) alphabet or 7-bit ASCII. PhosphorRTTY handles the standard configurations:

Baud rates: 45.45, 50, 75, 100 Bd (auto-detected or manual)
Shifts: 170, 450, 850 Hz (auto-detected or manual)
ITA2 (Baudot) and ASCII modes
USB signals, and LSB signals with mark and space inverted

AUTOMATIC SIGNAL DETECTION

The app automatically finds and locks onto RTTY signals:

AFC (Automatic Frequency Control) acquires and tracks drifting signals
Auto-baud detection identifies the transmission speed
Auto-shift detection determines the frequency separation
Squelch suppresses noise when no signal is present
Or disable any of these and tune manually for full control.

FOUR TABS

DECODE: the main teleprinter display. Decoded text appears character by character as it is received. The status panel shows baud rate, shift, mark and space frequencies, signal quality and lock state. Clear, pause and resume, start and stop.

SIGNAL: live signal analysis. FFT spectrum display (0 to 4 kHz) with mark and space cursors, scrolling waterfall, mark and space tone indicators, bit period histogram with baud rate markers, and a paper punch tape visualisation of the decoded data stream.

LOG: session history. Every decode session is saved with timestamp, duration, character count and the full decoded text. Copy, share or delete individual sessions, or export them all at once.

CONFIG: all parameters. Audio input gain, decode mode (auto or manual for baud, frequency and shift), ASCII mode, mark and…